OIC- I think I see the miscommunication WRT the flooding
"it didn't have anything to do with torrential rainfall landing in the city."
I see- you think I'm saying torrential rainfall flooded the city? No- here I think is the confusion. Ponchatrain is a watershed for the area. Katrina dumped like a faucet on the whole region (saturated hundreds of square miles with torrential rains), bloating ponchatrain, which in turn flooded the canals, which in turn started topping flood walls.
SELA, btw, was supposed to help prevent that- but probably would have been moot- as I said in my opriginal point. Thats why the levee system was part of SELA. Its not that they were as worried about rain ON NO, but rain causing ponchatrain to flood NO by breaching levess- which is exactly what happened.